Geae grinding machine



July 19, 1932.

C. H. SCHURR GEAR GRINDING MACHINE Original 'Ffliled Feb. 15, 1928 3 Sheets-Sheet m' m/Wir ja I5 Sheets-Sheet 2 III 43 014 ,llrll C. H. SCHURR GEAR GRINDING MACHINE (III Original Filed Feb. 15, 1928 July 19, 1932.

' Jmaentor July 19, 1932. .c, scHuRR GEAR GRINDING MACHINE 5 Sheets-Sheet 3 Original Filed Feb. 15, 1928 Reissued July 1 9, 1932 CHARLES H. SCHURR, OFCLE'VELANF, OHIO, ASSIGNORTO THE LEES-BRADNER (101111- PANY, OF CLEVELAND, OHIO, A CORPORATION OF OHIO L 1 GEAR eninnma MACHINE Original No. 1,751,104, dated March 18, 1930, Serial No. 254,382, filed February 15, 1928. Application for reissue filed-March 17, 1932. Serial No. 599,557.

This invention relates to gear grinding.

machines.

One of the objects of thlS 1I1VeIl131OI1 is to provide an improved gear grinding machine of the type in which the gear-to-be-ground or work gear, is rolled on a circle thereof and its teeth faces engage the face of a rotating grinding wheel with an-involute generating movement.

Another object is to provide a gear grinding machine of this class having improved inof spur gears; and in which the wheel may dexing means by which the work gear may be accurately and quickly indexed from one tooth to another. v Another object is to provide a gear grinding machine in which the grinding wheel maybe set to grind-gears of various pressure angles; and in which the wheel may be set with its face parallel to the rotational axis of the work gear to grinding the tooth faces also be set with its face at an angle to the said axis to grind-the tooth faces of right hand I or of left hand helical gears.

Another object is to provide a gear grindi'ng machine which, being adaptable to grind either spur or helical ears, is adaptable to rind both the spur aces and the helical aces-of the teeth of gear finishing tools such as are employed in the gear finishing method of-my Patent No. 1,642,179, Sept. 13, 1927; and which tools are fully-described in my appzlication, Serial No. 159,092, filed J an. 5, 19

Another object is to provide a gear grinding machine in which the generating movement of the work gear relative to the grinding wheel may be that which results from rolling a circle of the work gear on aline without slipping, whereby to generatively grind gear teeth with true involute faces;

and which may be adapted to give to the work gear the generative'movement which results from rolling a circle of the gear on a line and concurrently moving the line in its own directidn whereby to generatively grind on the gear tooth faces non-involute or modified involute profiles, the curve of which deviates from a true involute; and in which such modified involute curve may comprise a true involute'section and another curved section merging into each other without intersection; and in which these modified in The invention is fullydisclosed in the following description of one embodiment thereof, and in the accompanying drawings illustrating this embodiment, in which:

Fig. 1 is a top plan view partly in sectionand with some of the parts broken away, of

my improved gear grinding machine, taken approximately from the staggered plane 1 of Fig. 2, or the staggered plane l1 of Fig. 2 is aside elevational View partly in section and with some'of the parts broken away, taken approximately from the staggered plane 2-2 of Fig. 1 or from the plane 2-2 of Fig. 3;

Fig. 3 is a front elevational View partly in section and with some of the parts broken away and taken generally from the staggered plane 33 of Figs. 1 and 2;

Fig. 4 is a view taken similarly to Fig.2

and showing'a motor which is broken away from Fig. 2;

Fig. 5 is a top plan view of a cam device, shown also in front elevationalview in Fig. 2 Fig. 6 is a viewtaken from the plane 6 of Fig. 5;

Fig. 7 is a fragmentary view taken from the plane 7 of Fig. 3; y

A work spindle 1, carrying on one end a work gear or gear to be ground 2, and upon the other end a master gear 3, is mounted for rotary oscillation in a spindle housing 4, carried upon a slide 5 which slide is adapted to be reciprocated uponways 66 formed upon the main frame 7. A push-and-pull rod 8 has one end secured to the slide'5 at 9 and at the other end is connected, by means not "shown, to a power device for reciprocating the rod longitudinally to correspondingly reciprocate the slide 5 in a well known manner.

The teeth 10 of the master gear 3 are adaptedto mesh with the teeth 11 of a master rack v the master gear on astraight line without slipping. This rolling movement is transmitted to the work gear 2. The work gear 2 thus moves as if it were rolling upon an imaginary conjugate rack. The planular mounting and drive therefor, as well as the mechanism therefor may be employed.

Reference may be .had to my application, SerialNo. 561,219, filed May 15, 1922, a division' of which is now Patent No.'1,810,108,

issued June 16, 1931, for-one type of construction for thusicontrolling the grinding wheel and it is not deemed necessary to burden the face of a rotating-grinding wheel 16 is present description with details thereof. positioned (in a. manner to be described) so The column 17 rests'upon curved, pref- .that this face is coincident with the plane of one of the tooth faces of said imaginary rack.

' The teeth of the work gear 2 therefore slide upon the face of the grinding wheel with an involute generating movement and the pro-. files of the work gear teeth are ground to a true involute curvature. j i V The word p'lanular is used in describing the working face of the grinding wheel and this term is usedthroughout this specification as meaning capable of defining or producing a plane. The surface defined by the particular wheel illustrated is a plane normal to the axis of the wheel.-

. Rising from the base 7 of the machineisa column 17 for. supporting the, grinding.

wheel 16 in the ,'.followin manner. The grinding wheel 16 is ram, I mounted on a housing 18, carried upon a ead 19 which is adjustable in vertical planes and about a center 20, upon a vertically adjustable slide 21. B means of an operating shaft 22,

. gearing contained in a ear: housing 24 may square on the end at?) to receive a; tool,

be operated to adjustab y swivel or rock the Y Wheel housing 181aboutithe center 20. co-

ordinate'with this adjusting movement of the housing 18, the slide 21,. which is mounted -.upon vertical"ways-25'25 on the column 17,

may be raised and loweredthereon byga. screw 26'supported on the'column-17 and adapted, to be turned to propel .the slide 21 by means; of gearin ina gearshousing 27 and by a square-en ed operating. shaft 28 connected; therewith. Byraising orlowering the slide 21 and by rockin the head 19 aboutsthe cen-- ter 20 the plan ari face 15- of the grinding wheel may be adjusted-to any desiredpressule angle'with respect to thework ear, and to operate on any diameter-of wor gear. Tofurther a justtheposition of the. grinding wheel, the wheel is' movable longitudin I of axis of rotation by an adjusting hand" wh 29 connected by" mechanism; i (not shown) to aggpding wheel shaft withinthe erably horizontal, ways 31 and 32 on the main frame 7, and is bolted to the frame by bolts and fpreferably also intersecting the rotapassing-through the center of the work geartional axis'(extended) of the grinding wheel.

With this construction, the column 17 carrying the grinding positioned by'shding it around on the ways 31 and 32 and bolting. it in any adjustedposition; and as it is adj ustably moved from one positionto another the-grinding wheel will bebodily rotated about the said vertical axis.

When the column is adjusted to such a posiwheel may be adjustably" tion' thatthe planular face of the grinding wheel. is parallel to the axis of the work spindle, the .planular faced wheel may be adjusted .to bring its plane into coincidence with one of the; tooth faces of'thef above describedimaginary rack upon which a spur type work gear rolls; and when the column is adjusted to some other position, inwhich the. plane of the wheel faceis-iatan angle to the work spindle axis, the wheel facemay be adjusted to bring its plane'into coincidence with the face of one;ofthe imaginary rack-teeth on which a helical workj gear rolls.

. It will now be clearfthat the'planulah face 15 of the grinding wheel '16 the "bepo'sitional ly adjustedwithrelationto t e teeth of the workgear 2 to grindv faces thereon'which,"

inthe'rotati'onal plane's of the" work gear,"

are of involute. curvature, whether. said gear]- is as ur 'gear or whether-"it'is a right hand or'le hand helical gea n'fThe extent of the adjust'ability of jthefcolumn' 17' indicated in the. drawings is such as to. admit of the grinding of helical work gears with a range of helical angle-from-mero' degrees (spur-.

geazg to' 45 degrees crmore, or left an. 7- In my application,-'SerialNo.159,090, filed January 5', 1927, now Patent No/1,745,344, .4 issued January 28, 1930, I describe-a gear finishing tool which is in general of gearform, and the teeth of'which'have faces composed of a spur tooth portion combined with its one or more helical portions. It will be ap parent that such a gear'form tool may be veneratively ground upon the machine of this disclosure by successively setting the grinding wheel in the positions to grind spur and helical tooth faces.

By means of the mechanism thus far described, I provide a gear grinding machine for grinding involute faces on either spur or helical gears; and it will be noted that at any "helical angle adjustment of the grinding the helical angle.

wheel it may be adjusted for pressure angle and work gear diameter independently of Indexing mechanism Upon a bracket of the main frame 7 is secured, as by bolts 36, a vertical generally rectangular frame 37, angular in cross section. The frame is provided with ways 3838 upon which is mounted and adapted to be slid adjustably, vertically, an indexing mechanism housing support 39. The support 39 is provided with apair of horizontal guides 40 in which is suspended the flange.

ways 4141 of afreciprocable slide 42 to which is secured as by bolts 43 an indexmechanism-housing 44. The housing 44 is to change or adjust its vertical position on thus carried by the housing support 39 and movable in unison therewith on the ways 38 the machine. To effect this vertical adjustment, a screw 45 is provided, threaded into ing support 39 to be referred to later.

51, to the lower side of the housing 44 as is plainly shown. Mounted rigidly on a hori zontal shaft 52 in the housing 44 is an indexing cam device 14 shown in Figs. 2, 5 and 6. The cam device 14 is normally stationary but is adapted to be periodically oscillated through a limited angular movement by its shaft 52. The cam device 14 is generally semi cylindrical in form and has angularly arranged grooves'13 in the curved convex surface thereof which normally form a continuation of the tooth spaces of the rack 12.

,By a mechanism to be described, when the master gear. 3 rolls to the right, (as viewed in Fig. 2) and the teeth 10 of the gear leave the tooth spaces of the rack and enter the grooves 13 of the cam device 14, the cam device thereupon is set in motion and rocked or oscillated in one direction by means of the shaft 52; and the grooves 13 act upon the H gear teeth like cams and give a turning movement to the gear 3; The angular direction of the grooves 13 and the circumferential" dimensions thereof, and the extent of the oscillatory movement of the cam device 14 are so proportioned that when the cam device has 7 been turned or oscillated through approximately 180 degrees from its initial stationary position, it will have turned the gear 3 ahead one tooth. Themovement of the cam device 14 is then stopped by the said mechanism (to 76 be described) with the cam device in a second stationary position, and the gear 3 rolls back upon the'rack 12 in indexed relation thereto, and thereupon the camdevice 14 is set in motion and oscillated or rocked in the 80 reverse direction back to its original position. j

The mechanism for oscillating the cam device 14' will now be described. Secured to. the shaft 52 of the can1 device 14 is a gear 53 85 meshing with another gear 54 which is secured to a transmission shaft 55 mounted in the housing 44. The transmission shaft 55 extends horizontally outwardly through'the end wall 56 of the housing 44 and terminates in or is connected to an axially elongated gear or splined element 57. The elongated. gear 57 is rotatably mounted in bearings 58 supported by 'a bracket 59 on the rectangular.

frame 37.- The bracket 59 is provided with a vertically arranged opening. or guide 60 through which extends a vertically recipro cable rack 61-, the teeth of which mesh with the teeth of the elongated gear 57. The rack 61 has a longitudinal here through which exv100.

tends a threaded rod. 62; and by means of nuts 63 the vertical position of the rack 61-on the rod 62 may be adjusted in a well known manner. The threaded rod 62 is joined to a rectangular cam-follower-rod 64 extending 5 .downwardly therefrom as shown in Fig. 2 i

and entering a cam housing 65.

The lower end of the rod 64 carries a cam follower or'roller 66 adapted to run in the irregular groove 67 of a rotatable cam 68. The no groove 67 illustrated, is so shaped that in one 4 rotation of the cam 68 the cam follower rod 64 is. given a limited movement upwardly,: and then a dwell, and then a'corresponding movement downwardly, and then another dwell. The rotatable cam 68 is secured ,on' one end of a rotary drive shaft 69, as by a nut 70, and the shaft 69 is adapted to be rotated continuously in one direction and in timed relation to the reciprocatory movement of the movement which oscillates the shaft 55, gears 54 and 53, and cam device 14; and that by I 'properly shaping the cam groove 67! and properly timing the rotation thereof, the os- 7 cillatory movement of the cam device 14 may be caused to begin when the master gear3 is on the cam device 14 and at a point of the reciprocatory stroke of the slide suitable and desirable for indexing; and may be causedto'stop moving at a point of the slide stroke suitable for permitting the -master gear-to remesh with the master rack 12 on its 1 return movement.

1 gear may be keyed or otherwise angularly positioned on the work spindle in'a predetermined angular relatign thereto and in such cases in' settting np'the machine itxis often desirable to adjustahlyshift the'rack 12 longitudinally to position the work, gear relative to the grinding wheel. ..To effect this adjustment the following means is povided.

' On the right hand end (as viewed in Fig. 2)

of the indexing housing 44 is mounted a bracket 72 carrying-a horizontally arranged hand operatedpropelling screw 74 anchored in the bracket at 73 and threaded into the slide 42 at-75. By loosening the bolt 43Jand v turning the-screw 74, the housing 44 may be as rack 12, and in any adjusted .position the hou'n'm be lfi dbt'hte'- s1 g ay Secqre'y Xe y 1g $39. The cam shaft 80 carries on its outer end adjustably propelledto the right or to the left (inF-ig. 2) to'adjustably positionthe' the bolt: 43. 1

It is preferably tohave the master gear 3 of substantially the same diameter as the'work [gear 2, and therefore when different 'sizes'of work gear 2 areto be ground,. it is desirable to-raise or lower the rack 12 to adapt it to the corresponding different sizes of thefmaster 45 above describedmay be turned which will;

gears. To effect this adjustment; the screw move" the housing 44. vertically. Obviously f As'is well known it is sometimes de able to accurately grindthe faces of gear teeth the elongated gear 57 ,moves vertically wit the housing 44, and to accom'modatethe rack" .-61 to the different positions of the gear 57, the l rack 61 is made vertically, adjustable on the threaded rod 62 as above described. .y

to conform to a profile curvature which. is

I not a true involute but is a deviation from or modification thereof. In the gear grinder shown herein, means, which will now be described, is provided for giving. to the work gear a movement supplemental to its rolling movementon a line, a supplemental movement which'is equivalent to moving longitudinally the line on which a circle of the may beescured on the I described in my ment, is given a longitudin which the master gear 'n'sequently the gear rolls, during a part of the rolling movement.- The gear is thus caused to roll on a line without slipping during a portion of its tooth face generating movement and during this portion a true involute'is generated; but

at a preselected point in the generating movement, the line'on which the gear rolls is moved of an involute portion which merges into another curved 'portionpreferably without intersecting it.

A method and mechanismfor generating modified or non-involuteprofiles employing this principle in general is fully shownand application, 'Serial No.; 209,216, filed. July 29, 1927, in' connection with spur gears. Reference may be had thereto for a more compete discussion of the details of such a method and it is deemed unnecessary to expand the present description therewith. In the machine under discussion here, the underlying principle of that method is embodied in the following mechanism.

' As above described the reciprocable slide 42 has Ways 41' horizontally reciprocable, (fromside to side in Fig.2) in guides 40 on the housing support 39. Rising from the slide 42 is a pair of abutments. 76 and 7 7 between which'floats vertically a block 7 8-bored out. to receive an eccentric or rotary cam 79 by which the blockis supported. The cam 17 9 is mounted on a shaft 80 (with whichit may be formed integrally) and rotates about the axis'of the shaft in bearings 81 and 82 formed. in and stationary upon the housing.

a depending arm 83. 10 11 theloweror free end of the arm (Fig 7); is 'a roller or cam 1 follower 84, adapted to travel in a cam groove 85 of acam 86. Thecam 86 is made in the .form of a channel. bar mounted on apost 87 1 of the spindle housing 4 with it bodily and depresses the roller 84 giving a counterclockwise movement to the end of the arm 83 which. causes-it to act as a crank and turn the cam shaft 80. This turns 42 and thence through the housing 44 to rack 12 t0 thera k m ve t l gi tudinally. l v

This movement of the rackis transmitted. I to the master geai 3 in mesh therewith and is the supplemental 'involute-modifyingmovement hereinbefore referred to. Thus as the master gear 3 rolls on the rack 12, the" rack, at a certain pointjin the rolling move- 5 movement by work gear 2 is given asupplemental rotary movement; and this supplemental movement of the work gear causes it, to slide on the grinding Wheel in a manner to generate a rdfile which deviates from the true involute.

referably I hold the abutment 7 6 rigidly against the block 78 by a compression spring 88 one end of which abuts against the abutment 76 and the other end against the end of an adjusting screw 89 mounted in a suitably positioned boss in the Wall of the chamber 49 on the housing support '39. The thrust I of the spring 88 is taken up by the bearings 81 and 82 which support the cam shaft 80.

, The cam 79, the depending arm 83 and cam 86 may all be modified, or may be adjusted relatively to eachother as described in the above mentioned application, Serial No. 209,216, to produce involute profiles or any of the'various types of modified involute profiles shown and described in said, application,

'as well as others not shown.

It will now be'clear that by means of a machine described hereinbefore, I maygrind spur gears or right hand or left hand helical gears, the tooth profiles of which in the rotational planes of the gear may be of modified involute curvature, deviating from a trueiinvolute. In my application Serial No. 212,156; filed August 11, 1927, I describe a gear finishing method, in which a tool in general of gear form is employed, the teeth of which have faces composed of a spur tooth portion combined with one or more helical portions and the profile curve of each of which is composed of a true involute portion combined with and in some cases merging, without intersection, into another curved portion; and it will now be apparent that such a gear form tool may be generatively ground on the machine described hereinbefore by successively setting thegrinding wheel in the positions to grind modified involute spur and modified involutehelical tooth faces; and if desired the involute modification of the helical portion may be the same as that of the spur portion.

I claim:

' 1. In a gear grinding machine, a main frame, a gr nding wheel supporting column on the frame, a. planular faced grindlng wheel I rotatably mounted on the column, ways on the frame, a reciprocableslide on the ways, a

I 2. In a-gear grinding machine, a main frame, a grinding wheel supporting column on the frame, a planularfaced grinding wheel rotatably mounted on the column, ways on the frame, a reciprocable slide on the ways, a 6

work spindle rotatably mounted on the slide,

'means for reciprocating the slide and oscillatingthe work spindle to cause a work gear mounted. on the work spindle to roll on an imaginary conjugate rack, means for adjustably moving the column on the frame and for adjustably moving the planular face of the grinding wheel on the column to bring the wheel plane into coincidence with a tooth face of an imaginary right hand or left hand helical rack of helical angle, from zero degrees upward, the said column adjusting means including a curved guide way for the column on the frame.

3, In a gear grinding machine, a main frame, a grinding wheel supporting column wheel rotatably mounted on the column, ways on the frame, a reciprocable slide on the ways,

a work spindle rotatably mounted on the slide,

means for reciprocating the slide and oscillating the work spindle to cause a work gear mounted on the work spindle to roll on an imaginary conjugate rack, means for adjustably moving the column on the frame and for adjustably moving the planular face of the grinding wheel on the column toward and from the work gear and to vary its pressure angle, whereby to bring the wheel plane 7 into coincidence with a tooth face of an imaginary right hand or left hand helical rack of helical angle from zero degrees upward, the said column adjusting means ineluding a curved guide way for the column on the frame, circular about an axis through the center of the work gear.

4. In a gear grinding machine for grind ing helical gears ofhelical angle from zero on the frame, a planular faced grinding L upward right or left hand, a main frame, a

column on the frame, a planular faced'grin,d-

ing wheel rotatably mounted on the column, s

a work spindle rotatably mounted on the frame, means for reciprocating and oscillating the work spindle to cause a work gear mounted thereon to roll upon an imaginary helical rack, means for moving the. planular face of the grinding wheel to bring it into coincidence with a tooth face of the imaginary rack, and means for moving the column on the base to move the grinding wheelfi bodily in a circular path about an axis in a plane through the center of the work gear and at right angles to the gear axis to vary the helical angle.

,5. Ina gear grinding machine, a main frame, a column on the frame, a planular faced grinding wheel rotatably mounted on the column,-wayson the frame, areciprocatory slide on the ways, .a work spindle rotatably v mounted on the slide, a master spur-gear on.

the imaginary rack longitudinally.

* the work spindle, a master rack conjugate to i angles from zero upwards, right or left. I

the master gear supported on the frame, means for reciprocating the slide'to cause the master gear to roll on the master rack and for thus causing a work gear mounted on the work spindle to roll upon an imaginary conjugate rack, means comprising a circular guide way on the. frame for movin the column on the frame to move the grinding wheel bodily on a circular path about an axis in a plane through the center of the work gear and at right angles to the gear axis whereby to bring the planular face of the grinding wheel into coincidence'with a tooth face of various imaginary racks bearing helical 6. In a helical gear grind n machine, a main frame, a planular facedgrlnding wheel rotatably mounted on the frame, a work spindle, means for reciprocating and oscillating the work spindle to causea helical work gear mounted thereon to move with a rolling movement equivalent to rolling on an imaginary helical-rack conjugate thereto, means for adjustably moving the grinding wheel to a tooth face of said ima ary rack, whereby the rolling movement 0 the work gear may cause the wheel to generativ'ely grind an in: volute tooth facethereon, and means for con- 1 currently giving a supplemental rotary movement to the hehcal work gear to cause a part of the tooth face ground thereon to be of toward and from the work atively grlnd an involute tooth face thereon,-

' rotatably mounted on the modified involute curvature. I

7.'In a helical gear inding machine, a main frame, a planular aced igrrinding wheel ame, a work spindle, means for reciprocating and oscillating the work spindle to cause a helical work gear mounted thereon to move with a rolling movement equivalent to rolling on an imaghelical rack conjugate thereto,'means bring its lanular face into coinci ence with a tooth face of said ima'ginary rack, said means including means for moving the wheel er and for varying the pressure angle of fife wheel and for? revolving it bodily about an axis in. apline thru the gear center and at right angles to thegear axis, whereby the rolling movement of the work gear maycause the wheel to generand means for concurrently giving a. supplemental rotary movement to the helical work' gear to cause-a part of the tooth face ground thereon to beef modified involute curvature, said supplemental movement being equiva-' lent to that which would result from moving 8. 'In a helical gear grinding machine, a

'main frame,*acolumn on theframe, a'planu lar faced grindingjjwheel rotatably mounted .on the column, ways on the frame, aslide on grooves form again a continuation of the on the slide, a master rack on the frame, a master gear on the work spindle meshing with the rack and adapted to be rolled thereon; by reciprocation of the slide and to give to a-helical work gear mounted on the work spindle the movementof rolling on an imag inary conjugate helical rack, means forad-. justabl-y moving the planular face of the grinding wheel on the column, and for adjustably moving the column on the frame in a 7 curved path whereby to bring the planular face of the grinding wheel into coincidence I with a tooth face of the imaginary rack' at any helical angle thereof from zeroupwards right or left, means for reciprocating the slide on the ways, a work spindle on' the" slide, a master gear on-the work spindle, a master rack on the frame,'a normally sta tionary movable cam device on the frame, angularly disposed cam grooves on the cam 9 devicedisposed, when in said normally stationary position, to form a continuation of i the rack tooth spaces, means for reciprocat-- ing the slide in one direction to cause the master gear to roll on the master rack an to cause its teeth to roll from the tooth spaces of the rack into the grooves of the cam de--- vice, means for then moving the cam device to a second stationary position in which the Y rack tooth spaces, and the extent of said movement of the cam bein'g arranged to rotate the master gear one tooth pitch, whereby the mastergear may rollback upon the v rack on'the returnrec'iprocatory -movement .10 of the slide and in indexed relation thereto; v 10. In] anindexing mechanism a. work spindle, a master gear" on the work; spindle,

'a master rackupon which the master gear is adapted to berolled back and forth, a nor 1 .5 mallystationarycam device'adapted to be moved in a predetermined direction, cam

:grooves in the'device disposed at an Mgl to'its direction of movement,'th'e cam de ice being positioned relatively to thef-rack so 1 that in said stationary position the grooves fo La continuation of the. tooth ,spaces of the rack, means for rollingthe mastergear in one direction from the rack' on to theicam x device, means for moving the cam device to ,2, a second stationary 'position in which the grooves again form a continuation of therack-tooth spaces, and-for causing the cam grooves to rotate the'master ear one tooth f pitch, and meanslfor rolling t e master gear so I slide to cause the teeth of the work gear to slide upon the face of the grinding wheel with an involute generating movement and in the other direction back upon-the rack in indexed relation thereto, and means for returning the cam device to its original sta-' tionary position.

11. In an indexing mechanism, a work spindle,va master rack upon which the master gear is adapted to roll back and forth, a cam device oscillatable about an axis of rotation, acylindrical portion on the device co-axial with its rotational axis, helical grooves in the cylindrical portion, a normally stationary position forthe device in which said grooves form a continuation of the tooth spaces of the rack, means for rolling the gear from the rack on to the cam device, means for then oscillating the cam device about its axis to a second stationary position in which the grooves again form a continuation of the rack tooth spaces, the ex-, tent of movement and the angle of the grooves being such as to thereby rotate the master gear through one tooth pitch, means for rolling the master gear back upon the rack in indexed relation thereto and means for oscillating the cam device back to its original stationary position.

12. In a gear grinding machine, a main frame. ways on the frame, a slide on the ways, a work spindle on the slide, a master gear on the work spindle, a master rack on the frame, the master gear being adapted to roll to and fro on the rack when the slide is reciprocated, a' cam device oscillatable about an axis of rotation from one stationary position to another, a cam groove in the cam device which in the first stationary position forms a continuation of the master rack tooth spaces, means for periodically oscillating the cam device and for reciprocating theslide in timed relation whereby the master gear is caused to roll in one direction from the master rack on to the cam device in its first stationary position, and thecam device is then oscillated to its second stationary position to cause the cam groove to turn the master gear through one tooth pitch, and the master gear is then, rolled back upon the master rack in indexed relation thereto, and the cam device is then oscillated back to its original stationary position.

13. A gear grinding machine comprising a main frame. horizontal guide ways thereon, a table slidable upon said guide ways, a work spindle journalled on said table, means for reciprocating said table along said guide ways, rotating means including a master rack and a master gear imparting a rolling motion to said spindle as said table is reciprocated, a grindingwheel, a spindle carrying the grinding wheel and supported by the base, and means for relatively adjusting said spindles about a vertical axis.

14. A gear grinding machine comprising a main frame, horizontal guide ways thereon, a table slidable upon said guide ways,

a work spindle journalled on said tabl, means for reciprocating said table along said guide ways, a grinding wheel, a spindle carrying,

15. A gear grinding machine comprising a main frame, horizontal guide Ways thereon, a table slidable upon said guide ways, a work spindle ournalled on said table means for reciprocating said table along said guide ways, a grinding wheel, a spindle carrying the grinding wheel and supported by the base, a master gear fixed to said work spindle, a master rack meshing with said master gear, an indexing member onto which said master gear rolls at one end of the reciprocation of said table, means moving said indexing member to impart a rotational increment to said spindle, and means for relatively adjusting said spindles about a ver tical axis.

CHARLES H. soHURR. 

